But after all what is the difference between UVA and UVB?

The ultraviolet (UV) cover only 5% of the energy that reaches the Earth and can be classified into UVA, UVB and UVC.

UVA
Cross the epidermis to the melanocytes (melanin producing cells located in the lower layer of the epidermis – the basal layer), where trigger the process of melanogenesis, i.e.production of melanin (responsible for the color of skin, hair and eyes), being therefore designated melanogenic radiation.

Advantages of UVA: responsible for direct tanning of the skin.

Disadvantages of UVA: premature cutaneous photoaging, dehydration of the skinand in the long run, enhances the appearance of cutaneous melanonas.

UVB
Also designated of erythematogenic radiation, are responsible for the formation of acute cutaneous erythema (red, painful nodules caused by capillary vasodilation, commonly referred to as Scalds).

Disadvantages of UVB: the long exposures repeated and exacerbate the negative effects of UVA and cause structural changes in dermal cells (mutations) that may result on cutaneous carcinomas (skin type of cancer most common).